Process dependent graphene/MnO2 composites for supercapacitors
Process dependent graphene/MnO2 composites for supercapacitors
复制标题
DOI：
10.1016/j.cej.2013.06.095
复制
发表时间：
2013-08
影响因子：
15.1
通讯作者：
Myeongjin Kim;Yongseon Hwang;Jooheon Kim
中科院分区：
文献类型：
--
作者：
Myeongjin Kim;Yongseon Hwang;Jooheon Kim
采用不同的反应工艺制备了两种类型的石墨烯/MnO2复合材料。S1的合成如下：首先，利用不同的官能团(GO/MnO2)在GO片上形成纳米针状MnO2。第二阶段采用浸渍法制备GO/MnO2为石墨烯/MnO2(S1)。采用不同的反应顺序合成了S2：首先，氧化石墨烯被还原为石墨烯，并在石墨烯上形成纳米针状MnO2。用X射线衍射仪、场发射扫描电子显微镜、X射线光电子能谱和热重分析等手段对所制备的复合材料的形貌和微观结构进行了表征。表征表明，S_1复合材料中的纳米针状MnO_2结构均匀地分散在石墨烯片层上，而S_2复合材料中的MnO_2由于缺乏官能团而形成聚集体。以1M Na2SO4水溶液为电解液，在三电极实验装置上用循环伏安法、恒电流充放电测试和电化学阻抗谱测试了S1和S2电极的电容性能。在S−1的10−下，S1电极的比电容高达327.5 F g−1，高于S2电极的比容(229.9 F g−1)。可以预见，还原过程后在GO表面形成纳米针状MnO2可能是一种很有前途的超级电容器电极的制备方法。
Two types of graphene/MnO2composites were synthesized by different reaction procedures. S1 was synthesized as follows: first, nanoneedle MnO2was formed on the GO sheets using various functional groups (GO/MnO2). In the second stage, GO/MnO2was reduced to graphene/MnO2(S1) via the dipping method. S2 was synthesized using a different reaction order: first, graphene oxide was reduced to graphene and nanoneedle MnO2was formed on graphene sheets. The morphology and microstructure of the as-prepared composites were characterized by X-ray diffractometery, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Characterization indicated that the nanoneedle MnO2structures in the S1 composite were homogeneously dispersed on graphene sheets, whereas MnO2in the S2 composite formed aggregates due to absence of functional groups. The capacitive properties of S1 and S2 electrodes were measured using cyclic voltammetry, galvanostatic charge/discharge tests, and electrochemical impedance spectroscopy in a three-electrode experimental setup with an aqueous solution of 1 M Na2SO4as the electrolyte. The S1 electrode exhibited a specific capacitance as high as 327.5 F g−1at 10 mV s−1, which was higher than that of the S2 electrode (229.9 F g−1). It is anticipated that the formation of nanoneedle MnO2on the GO surface following the reduction procedure could be a promising fabrication method for supercapacitor electrodes.